Evaluating piezoelectric constant d₃₁ of films deposited on silicon using low frequency-actuated piezoelectric cantilever structures

Piezoelectric coefficients of films deposited on silicon are surprisingly expensive to measure using experiments commonly found in literature. A low-cost method of approximating the small-signal piezoelectric coefficient d₃₁ for a film by comparing data from a single laser-doppler vibrometer measurement and a numerical model is presented. This method is useful for directly evaluating the quality of a piezoelectric film. Relevant properties of piezoelectric materials are introduced, and pitfalls of prior testing methods are discussed. An analytical model of the test is developed to provide insight into critical test parameters. The test is validated by comparing the numerical and the analytical model, by comparing experimental results to film x-ray diffractometry measurements, and by building opportunities for validation into the experiment. Explicit experimental validation is deemed too expensive and unnecessary for the immediate needs of the author. The method is also applied to evaluate the piezoelectric properties of several AlN films developed using varying fabrication parameters. Results are used to improve the fabrication process of an AlN film on silicon for use in piezoelectric sensor prototypes